Phosphorylation of glycogen synthase and of the beta subunit of eukaryotic initiation factor two by a common protein kinase.
A protein kinase from rabbit reticulocytes, able to phosphorylate the beta subunit of eukaryotic initiation factor 2 (eIF-2), has been demonstrated to phosphorylate also glycogen synthase. A glycogen synthase kinase (PC0.7) from rabbit skeletal muscle has been shown to phosphorylate the beta subunit of eIF-2. Comparison of highly purified preparations of the two protein kinases has indicated several similarities of properties. 1) Both enzymes were associated with two major polypeptide species, alpha (Mr = 43,000) and beta (Mr = 25,000), and exhibited apparent native molecular weights of 176,000-180,000 by gel filtration and 130,000-140,000 by sucrose density gradient sedimentation. 2) Both enzymes phosphorylated glycogen synthase, eIF-2 beta, phosvitin, and casein and were effective in utilizing GTP and ATP as phosphoryl donors. 3) Both enzymes displayed the same chromatographic behavior on phosvitin-Sepharose, phosphocellulose, and DEAE-cellulose. 4) Both enzymes underwent an autophosphorylation of the beta polypeptide when incubated with ATP and Mg2+. On the basis of these and other properties, we propose that the two protein kinases, if not identical, are very similar enzymes.
D000818:Animals; D015852:Eukaryotic Initiation Factor-2; D006006:Glycogen Synthase / Q000378:metabolism*; D046911:Macromolecular Substances; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology*; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology*
D015852:Eukaryotic Initiation Factor-2; D046911:Macromolecular Substances; D010448:Peptide Initiation Factors; D011506:Proteins; D006006:Glycogen Synthase; D011494:Protein Kinases